From 558ca359b80cbfe4331c2f667935da668bd25a08 Mon Sep 17 00:00:00 2001
From: fufesou <linlong1266@gmail.com>
Date: Sun, 4 Oct 2026 20:48:56 -0700
Subject: [PATCH] fix: distinguish AltGraph from ordinary Alt shortcuts

Signed-off-by: fufesou <linlong1266@gmail.com>
---
 src/keyboard/shortcuts.rs | 27 ++++++++++++++++++++++-----
 src/platform/linux.rs     | 29 +++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/src/keyboard/shortcuts.rs b/src/keyboard/shortcuts.rs
index 5423af5a3..23544f30b 100644
--- a/src/keyboard/shortcuts.rs
+++ b/src/keyboard/shortcuts.rs
@@ -150,10 +150,6 @@ pub fn match_normalized<'a>(key: &str, mods: &[Modifier], b: &'a Bindings) -> Op
 pub fn normalize_modifiers(alt: bool, ctrl: bool, shift: bool, command: bool) -> Vec<Modifier> {
     // iOS shares Apple's keyboard semantics with macOS — recording dialog
     // already treats iOS as `_isMac`, so the matcher must too.
-    //
-    // AltGr conflation: `get_modifiers_state` ORs Alt and AltGr, so an
-    // AltGr+key press satisfies `Modifier::Alt`. Theoretical collision only;
-    // fix at `get_modifiers_state` if a real bug surfaces.
     let mut v = Vec::new();
     if cfg!(any(target_os = "macos", target_os = "ios")) {
         if command { v.push(Modifier::Primary); }
@@ -333,7 +329,28 @@ pub fn match_event(event: &rdev::Event) -> Option<String> {
     let (alt, ctrl, shift, command) =
         crate::keyboard::client::get_modifiers_state(false, false, false, false);
     let mods = normalize_modifiers(alt, ctrl, shift, command);
-    match_normalized(&key_name, &mods, &bindings).map(str::to_owned)
+    let action = match_normalized(&key_name, &mods, &bindings)?;
+    // AltGraph is text input, not the ordinary Alt recorded in a shortcut.
+    // Keep the shared modifier snapshot unchanged for remote key encoding.
+    #[cfg(target_os = "windows")]
+    if unsafe { super::IS_0X021D_DOWN }
+        && super::MODIFIERS_STATE.lock().unwrap().get(&rdev::Key::AltGr) == Some(&true)
+    {
+        return None;
+    }
+    #[cfg(target_os = "linux")]
+    if super::MODIFIERS_STATE.lock().unwrap().get(&rdev::Key::AltGr) == Some(&true) {
+        match crate::platform::linux::right_alt_is_level3_shift() {
+            Ok(true) => return None,
+            Ok(false) => {}
+            Err(err) => {
+                hbb_common::throttled_log!(std::time::Duration::from_secs(5), warn,
+                    "Cannot identify AltGraph for keyboard shortcuts: {}", err);
+                return None;
+            }
+        }
+    }
+    Some(action.to_owned())
 }
 
 #[cfg(feature = "flutter")]
diff --git a/src/platform/linux.rs b/src/platform/linux.rs
index 169e63021..8f6f3068c 100644
--- a/src/platform/linux.rs
+++ b/src/platform/linux.rs
@@ -302,6 +302,35 @@ thread_local! {
     static DISPLAY: RefCell<*mut c_void> = RefCell::new(unsafe { XOpenDisplay(std::ptr::null())});
 }
 
+pub fn right_alt_is_level3_shift() -> ResultType<bool> {
+    use hbb_common::x11::{keysym, xlib};
+    const XKB_USE_CORE_KBD: c_uint = 0x0100;
+    // A fresh connection avoids Xlib's stale keymap cache after a layout switch.
+    // This query runs only for a matched chord with physical Right Alt held.
+    let display = unsafe { xlib::XOpenDisplay(std::ptr::null()) };
+    if display.is_null() {
+        bail!("X display unavailable");
+    }
+    let result = (|| {
+        let code = rdev::linux_keycode_from_key(rdev::Key::AltGr)
+            .ok_or_else(|| anyhow!("Right Alt has no X keycode"))?;
+        let mut state: xlib::XkbStateRec = unsafe { std::mem::zeroed() };
+        let status = unsafe { xlib::XkbGetState(display, XKB_USE_CORE_KBD, &mut state) };
+        if status != c_int::from(xlib::Success) {
+            bail!("XkbGetState failed: {}", status);
+        }
+        let symbol = unsafe {
+            xlib::XkbKeycodeToKeysym(display, code as _, state.group.into(), 0)
+        };
+        // Physical Right Alt is ordinary Alt on layouts such as US English.
+        Ok(matches!(symbol as u32, keysym::XK_ISO_Level3_Shift
+            | keysym::XK_ISO_Level3_Latch | keysym::XK_ISO_Level3_Lock
+            | keysym::XK_Mode_switch))
+    })();
+    unsafe { xlib::XCloseDisplay(display) };
+    result
+}
+
 // X11 error event structure for the custom error handler.
 // See: https://www.x.org/releases/current/doc/libX11/libX11/libX11.html#Using-the-Default-Error-Handlers
 #[repr(C)]